Alkyl acrylate-polyalkyleneimine sizing composition and method of sizing paper therewith

ABSTRACT

A COMPOSITION OF AN ALKYL ACRYLATE HAVING 22 TO 30 CARBON ATOMS IN THE ALKYL GROUP SUCH AS DOCOSYL OR OCTACOSYL ACRYLATE AND A POLYALKYLENEIMINE OR POLY (NMETHYLAKYLEMEIMINE) OR MIXTURES THEREOF HAVING 2 TO 3 CARBON ATOMS IN EACH ALKYLENE BRIDGE SUCH AS POLYETHYLENEIMINE OR POLY (N-METHYLPROPYLENEIMINE). THE COMPOSITION IS DISPERSED WITHIN THE WET PULP AS A SIZE IN THE FORMATION OF A PAPER WEB.

Unitcd States Patent thee Public Int. Cl. D2111 3/00; D21h 3/ 40 US. Cl. 162-168 16 Claims ABSTRACT OF i12 DISCLOS A composition of an alkyl acrylate having 22 to 30 carbon atoms in the alkyl group such as docosyl or octacosyl acrylate and a polyalkyleneimine or poly (N- methylalkyleneimine) or mixtures thereof having 2 to 3 carbon atoms in each alkylene bridge such as polyethyleneimine or poly (N-methylpropyleneimine). The composition is dispersed within the wet pulp as a size in the formation of a paper web.

This application is a continuation-in-part of application Ser. No. 500,209 filed Oct. 21, 1965, now Pat. No. 3,461,029.

This invention relates to novel sizing compositions, to methods of sizing cellulosic paper substrates and to the sized cellulosic substrates.

The term cellulosic paper substrate as used herein includes sheet-like masses and molded products made from fibrous cellulosic materials which can be derived from both natural and synthetic sources. Also included are sheet-like masses and molded products prepared from combinations of cellulosic and non-cellulosic materials derived from synthetics such as polyamides, polyesters and polyacrylic resin fibers as well as from mineral fibers such as asbestos and glass.

Cellulosic substrates are often sized with various materials for the purpose of increasing their resistance to water as well as to other types of aqueous solutions. These materials are referred to as sizes or sizing agents and they can be introduced during the actual paper-making operation wherein the process is known as internal or wet end sizing or they can be applied to the surface of the finished cellulosic paper substrate, in which case the process is known as external or surface sizing.

Various water repellent materials have been utilized as sizing agents. These include rosin, mixtures of rosins with waxes, wax emulsions, ketene dimer emulsions, fluorcarbons, fatty acids, complexes of chromium or alumium chloride, long chain thermoplastic copolymers, as well as some thermosetting condensation resins. Although all of these materials are effective to some degree under certain conditions, their use is nonetheless subject to one or more limitations.

For example, although rosin is relatively low in cost and readily available, it has poor resistance to alkaline solutions and cannot be used for the sizing of neutral or alkaline pulp. It is inoperable with the latter, since it must ordinarily be used in combination with alum or an acidic aluminum ion donor, which is present for the purpose of precipitating and setting the sodium rosinate, i.e. the rosin soap, onto the fibers. The use of alum for this purpose is, however, precluded under neutral or alkaline conditions. This is a definite disadvantage since the paper produced from neutral and alkaline pulp has 3,574,053 Fatented Apr. 6, 1971 been found to have higher strength, greater stability and superior aging characteristics in comparison with the paper prepared from acidic pulp. A further disadvantage of some sizing agents is that a considerable degree of heat curing is required to develop their full effectiveness. Thus, in using these materials, full effectiveness and full sizing value may not be obtained immediately after formation and drying of cellulosic paper substrates.

In accordance with this invention, it has now been found that the use of certain acrylate/polyalkyleneimine compositions as sizing agents with cellulosic paper substrates results in the preparation of cellulosic paper sub strates which display an unusually high degree of water resistance. Of prime importance is the fact that the successful use of the sizing compositions of this invention is not restricted to any particular pH range, thus allowing their utilization in the treatment of neutral and alkaline pulp as well as acidic pulp. The sizing compositions of this invention can also be used in combination with alum as well as with any of the pigments, fillers and other ingredients which are normally added to paper. Still another advantage of the sizing compositions of this invention is that they may be used in conjunction with other sizing agents so as to obtain additive sizing effects. A further advantage of the sizing compositions of this invention is that only mild drying or curing conditions are required to develop full sizing value.

The sizing compositions of this invention comprise at least one alkyl acrylate having from 22 to 30 carbon atoms in the alkyl group and a polyalkyleneimine or poly(N-methylalkyleneimine), or mixtures thereof, having from 2 to 3 carbon atoms in each alkylene bridge. The alkyl acrylate to polyalkyleneimine or poly(N- methylalkyleneimine) weight ratios can range from about 1:10 to about 10:1. The preferred ratio is from about 1:1 to about 1:3.

As mentioned above, the sizing compositions of this invention can be used as internal sizing agents or as surface sizing agents. When used as internal sizing agents, the sizing compositions are incorporated into the pulp by addition to aqueous suspensions of paper stock or furnish in the beater stock chest, Jordon engine, fan pump, head box or at any other suitable point ahead of the wire or a sheet forming stage. When used as an external sizing agent, the methods for applying the compositions of this invention are well known in the art. Such methods include the use of horizontal and vertical size presses, tub sizing, spraying, and roller and rod coating.

When the sizing compositions of this invention are used as internal sizing agents, they can be mixed together into one emulsion prior to their addition to the aqueous pulp slurry or, if desired, the two components can be added separately. When the sizing compositions of this invention are used as external sizing agents, they can be applied in the form of an aqueous emulsion or solution of the two components, or they can be admixed with a starch and formed into a starch/alkyl acrylate/polyalkyleneimine aqueous emulsion for the purpose of application.

Polyalkylene imines useful in the sizing composition of this invention are water soluble and are available commercially as aqueous solutions. The alkyl acrylates useful in the sizing compositions of this invention are water insoluble and must, therefore, be dispersed prior to admixture with the polyalkyleneamine and/or starch or starch derivatives. An aqueous dispersion of the alkyl acrylates can be formed by any of the methods well known in the art. For example, an aqueous emulsion can be prepared by admixture of the acrylate, optionally an organic solvent for the acrylate, a surface active agent and water. In some cases vigorous mechanical shearing action is also employed. Examples of suitable surface active agents include the conventional soaps, such as salts of long-chain carboxylic acids; sulfonated animal, vegetable and mineral oils; rosin soaps such as salts of abietic acids; sulfuric acids, salts of high molecular Weight organic compounds; algin soaps and ethylene oxide condensated with fatty acids, alkyl phenols or mercaptans.

The starch or starch derivatives with which the sizing compositions of this invention can be admixed for external sizing applications are those which are commonly used in cellulosic paper substrate surface sizing and coating applications, including corn starch, potato starch, sago starch, wheat starch, tapioca starch as well as the various starch products and derivatives including British gums, enzymes, converted starches, hydroxyethylated starches, oxidized starches, and cationic starches having quaternary ammonium or other a mine salt groups therein.

The sizing compositions of this invention can be mixed in aqueous dispersed form with the starch or starch derivative. In general, from about 1% to about 20% of the sizing composition can be used with the starch based on the Weight of the starch to which it is added. Preferably, about 2% to about of the sizing composition based on the weight of the starch is used. The sizing compositions of this invention can be mixed with the starch or starch derivative before cooking and cooked therewith or they can be mixed with the starch after cooking.

The percent solids content of the solution used for external sizing when starch is present will generally range from about 1 to solids. It is preferred to use a solution containing from about 3% to about 10% solids.

The sizing compositions of this invention can be successfully utilized for the sizing of cellulosic paper substrates prepared from all types of both cellulosic and combinations of cellulosic with non-cellulosic fibers. The cellulosic fibers which can be used include bleached and unbleached sulfate, bleached and unbleached sulfite, bleached and unbleached soda, neutral sulfite, groundwood, and any combination of these fibers. These designations refer to wood pulp fibers which have been prepared by means of a variety of processes used in the pulp and paper industry. In addition, synthetic fibers of the viscose rayon or regenerated cellulose type, or natural fibers such as cotton can be used.

All types of pigments and fillers can be added to the paper which is to be sized with the sizing compositions of this invention. Such materials include clay, talc, titanium dioxide, calcium carbonate, calcium sulfate, and diatomaceous earth. Other additives including alum as well as other sizing agents can also be used with the sizing agents of this invention.

With respect to proportions, the sizing compositions of this invention can be employed in amounts ranging from about 0.05% to about 10% based on the dry weight of the pulp in the finished cellulosic paper substrate. Within this range, the specific amount which will be used depends for the most part upon the type of pulp which is being utilized, the specific operating conditions, as Well as the particular end use for which the cellulosic paper substrate is destined. Thus, for example, paper which will require good Water resistance or ink holdout will necessitate the use of a higher concentration of sizing composition than paper which will be used in applications Where excess sizing is not required.

The alkyl acrylates useful in the sizing compositions of this invention can be prepared in accordance with the methods set forth in US. Patent 3,100,794 for the preparation of alkyl propiolates. They also can be prepared in accordance with the method set forth in an article by Rehberg et al. in the Journal of American Chemical Society 66, 1203 (1944), or according to methods listed in Organic Syntheses, Collective Volume 3, pages 146 148.

The polyalkyleneimines useful in the sizing compositions of this invention are the polymerization products of ethyleneimine or derivatives thereof and are described, for example, in US. Patent 2,182,386. The poly(N-methylalkyleneimines) are the polymerization products of N- methylethyleneimine, N-methylpropyleneimine or mixtures thereof. It is preferred that the polyalkyleneimine and poly(N-methylalkyleneimines) have a molecular weight of at least 1000.

The following example will further illustrate the invention, but the invention is not restricted thereto.

EXAMPLE 1 An unsized sheet of basis weight of 44 lb./ 3300 sq. ft. is prepared from a 50% hardwood and 50% softwood pulp slurry, refined to a Canadian Standard Freeness of 375 and formed into paper at pH 7 with no chemical additives. The unsized sheet has a Gurley porosity of 10 seconds.

An alkyl acrylate emulsion is prepared by admixing 1 part of the acrylate with 100 parts of a cooked aqueous solution containing two parts Cato-8 starch and 0.2 parts of sodium lignin sulfonate and 100 parts of water at 50 C. with vigorous agitation.

A 10% by weight of aqueous Stayco-A starch slurry is cooked at to C. for 15 minutes and allowed to cool. The starch solution is admixed with a sufficient amount of alkyl acrylate emulsion, polyethyleneimine (PEI 600, Dow Chemical Co.) and water to form a starch/alkyl acrylate/polyethyleneimine sizing composition comprising 3% by weight of starch based on the composition, 5% by Weight of polyethyleneimine based on the starch in the composition, and 5% by weight of the alkyl acrylate based on the starch in the composition. The paper sheets are dipped into the starch/alkyl acrylate/ polyethyleneimine sizing composition and then run through a size press roll. The pick up of the aqueous starch/alkyl acrylate/polyethyleneimine composition is 0.96 g. per g. of paper. The sheets are dried or cured and tested for water resistance by the ink penetration test which comprises floating a sample of the sized paper on a standard ink having a pH of 1.5 and observing the time required for the first trace of blue coloration to appear on the surface of the test paper. Results and further details are given below in Table 1.

1 Drum dried at 204 F. for 30 seconds- 2 Cured at F. for 5 minutes.

EXAMPLE 2 Cellulose pulp used to make paper was slurried with water to give 2% pulp solids and refined to 480 520 CFS. Polyethyleneimine (PEI 600, Dow Chemical Co.) is added to the pulp slurry in the amount of 1% based on the weight of dry pulp. The pH of the aqueous pulp slurry is adjusted to 9 and docosyl acrylate emulsion is added to the pulp slurry in an amount of 1% acrylate based on the weight of dry pulp. Handsheets are prepared from the pulp on a Noble & Wood Machine and dried at 204 C. for 90 seconds. The sized sheets are tested for ink penetration by the method set forth in Example 1 above. The average ink resistance time for 10 samples is found to be greater than about 1000 seconds.

The embodiments of this invention in which an exclusive property or privilege is claimed are defined as follows:

1. Composition comprising at least one alkyl acrylate having from 22 to 30 carbon atoms in the alkyl group and a polyalkyleneimine or poly(N-methylalkyleneimine), or mixtures thereof, having from 2 to 3 carbon atoms in each alkylene bridge.

2. Composition of claim 1 wherein the alkyl acrylate is docosyl acrylate and the polyalkyleneimine is polyethyleneimine.

3. Composition of claim 1 wherein the alkyl acrylate is octacosyl acrylate and the polyalkyleneimine is polyethyleneimine.

4. Composition of claim 1 wherein the alkyl acrylate and the polyamine are present in weight ratios of from about 1:10 to about 10:1.

5. Cellulosic substrate sized with a sizing composition comprising an alkyl acrylate having from 22 to 30 carbon atoms in the alkyl group and a polyalkyleneimine or poly(N-methylalkyleneimine), or mixtures thereof, having from 2 to 3 carbon atoms in each alkylene bridge.

6. Cellulosic substrate of claim 5 wherein the alkyl acrylate is docosyl acrylate and the polyalkyleneimine is polyethyleneimine.

7. Cellulosic substrate of claim 5 wherein the alkyl acrylate is octacosyl acrylate and the polyalkyleneimine is polyethyleneimine.

8. Cellulosic substrate of claim 5 wherein the alkyl acrylate and the polyamine are present in weight ratios of from about 1:10 to about :1.

9. Method of sizing cellulosic paper substrates which comprises dispersing within the wet pulp prior to the conversion of the wet pulp into a dry substrate, a composition comprising at least one alkyl acrylate having from 22 to 30 carbon atoms in the alkyl group and a 20 polyalkyleneimine or poly(N-methylalkyleneimine), or mixtures thereof, having from 2 to 3 carbon atoms in each alkylene bridge.

10. The method of claim 9 wherein the alkyl acrylate is docosyl acrylate and the polyalkyleneimine is polyethyleneimine.

11. The method of claim 9 wherein the alkyl acrylate is octacosyl acrylate and the polyalkyleneimine is polyethyleneimine.

12. The method of claim 9 wherein the alkyl acrylate and the polyamine are present in weight ratios of from about 1:10 to about 10:1.

13. The method of sizing cellulosic paper substrates which comprises contacting a formed substrate with a composition comprising at least one alkyl acrylate having from 22 to 30 carbon atoms in the alkyl group and a polyalkyleneimine or poly(N-methylalkyleneimine), or mixtures thereof, having from 2 to 3 carbon atoms in each alkylene bridge.

14. The method of claim 12 wherein the alkyl acrylate is docosyl acrylate and the polyalkyleneimine is polyethyleneimine.

15. The method of claim 13 wherein the alkyl acrylate is octacosyl acrylate and the polyalkyleneimine is polyethyleneimine.

16. The method of claim 13 wherein the alkyl acrylate and the polyamine are present in weight ratios of from about 1:10 to about 10:1.

References Cited UNITED STATES PATENTS 3,350,340 10/1967 Sounksen 162-168 3,419,465 12/1968 Maruta 162-168 3,461,029 8/1970 Hine et al. 162168 S. LEON BASHO'RE, Primary Examiner R. H. ANDERSON, Assistant Examiner US. Cl. X.R. 

